Apparatus and method for linear mixing tube assembly

ABSTRACT

A mixing tube assembly having an inlet end and an outlet end and being adapted for use in a burner assembly. The mixing tube assembly comprises a substantially cylindrical outer wall which defines an interior open space. The mixing tube assembly also comprises a turbulator that is disposed in the interior open space defined by the substantially cylindrical outer wall and a flow straightening device that is disposed downstream from the turbulator. A method for mixing fuel and air in a burner assembly comprising providing a mixing tube assembly. The preferred method also comprises conveying fuel and air from the inlet end of the mixing tube assembly to the outlet end of the mixing tube assembly and straightening the gaseous fuel and air mixture flow in the mixing tube assembly.

CROSS-REFERENCES TO RELATED APPLICATIONS/PATENTS

This application relates back to and claims the benefit of priority fromU.S. Provisional Application for Patent No. 61/744,690 titled “Apparatusand Method for a Linear Gas Tube” and filed on Oct. 2, 2012, and is acontinuation-in-part application of U.S. patent application Ser. No.13/422,228 titled “Apparatus and Method for Mixing Tube Assembly” andfiled on Mar. 16, 2012 which relates back to and claims the benefit ofpriority from U.S. Provisional Application for Patent No. 61/465,215titled “Apparatus and Method for Mixing Tube With a Swirler” and filedon Mar. 16, 2011.

FIELD OF THE INVENTION

The present invention relates generally to burner assemblies, andparticularly to devices adapted to mix air and fuel in burnerassemblies.

BACKGROUND AND DESCRIPTION OF THE PRIOR ART

It is known to mix air and fuel in burner assemblies. Conventionaldevices used to mix air and fuel in burner assemblies, however, sufferfrom one or more disadvantages. For example, conventional devices usedto mix air and fuel in burner assemblies are undesirably large andexpensive to manufacture and operate. In addition, conventional devicesused to mix air and fuel do not efficiently or sufficiently mix air andfuel together. Conventional devices used to mix air and fuel also do notstraighten the gaseous fuel and air mixture flow in the mixing tube soas to minimize or eliminate turbulence between flows from other mixingtube assemblies.

It would be desirable, therefore, if an apparatus and method for adevice adapted to mix air and fuel in a burner assembly could beprovided that would reduce the size and cost of manufacture andoperation. In addition, it would also be desirable if such an apparatusand method could be provided that would mix air and fuel moreefficiently, completely and uniformly. It would also be desirable ifsuch an apparatus and method could be provided that would straighten thegaseous fuel and air mixture flow in the mixing tube so as to minimizeor eliminate turbulence between flows from other mixing tube assemblies.

Advantages of the Preferred Embodiments of the Invention

Accordingly, it is an advantage of the preferred embodiments of theinvention claimed herein to provide an apparatus and method for a deviceadapted to mix air and fuel in a burner assembly that reduces the sizeand cost of manufacture and operation. It is also an advantage of thepreferred embodiments of the invention claimed herein to provide anapparatus and method that mixes air and fuel more efficiently,completely and uniformly. Further, it is an advantage of the preferredembodiments of the invention claimed herein to provide an apparatus andmethod that straightens the gaseous fuel and air mixture flow in themixing tube so as to minimize or eliminate turbulence between flows fromother mixing tube assemblies.

Additional advantages of the preferred embodiments of the invention willbecome apparent from an examination of the drawings and the ensuingdescription.

EXPLANATION OF TECHNICAL TERMS

As used herein, the term “flow straightening device” means any device,mechanism, assembly or combination thereof that is adapted to facilitatethe flow of air, fuel or a mixture of air and fuel in a burner assemblyin a direction generally parallel to the longitudinal axis of the burnerassembly.

As used herein, the term “turbulator” means swirlers, curved vanes,bluff bodies, tabs, lips, surface treatments and/or any other suitabledevice, mechanism, assembly or combination thereof which is adapted tomix fuel and air.

SUMMARY OF THE INVENTION

The apparatus of the invention comprises a mixing tube assembly havingan inlet end and an outlet end and being adapted for use in a burnerassembly. The mixing tube assembly comprises a substantially cylindricalouter wall which defines an interior open space. The mixing tubeassembly also comprises a turbulator that is disposed in the interioropen space defined by the substantially cylindrical outer wall and aflow straightening device that is disposed downstream from theturbulator.

The method of the invention comprises a method for mixing fuel and airin a burner assembly. The preferred method comprises providing a mixingtube assembly having an inlet end and an outlet end. The preferredmixing tube assembly comprises a substantially cylindrical outer wallthat defines an interior open space. The preferred mixing tube assemblyalso comprises a turbulator that is disposed in the interior open spacedefined by the substantially cylindrical outer wall and a flowstraightening device that is disposed downstream from the turbulator.The preferred method also comprises conveying fuel and air from theinlet end of the mixing tube assembly to the outlet end of the mixingtube assembly and straightening the gaseous fuel and air mixture flow inthe mixing tube assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

The presently preferred embodiments of the invention are illustrated inthe accompanying drawings, in which like reference numerals representlike parts throughout, and in which:

FIG. 1 is a perspective view of the preferred mixing tube assembly inaccordance with the present invention.

FIG. 2 is a partial sectional perspective view of an exemplary burnerassembly including a plurality of the preferred mixing tube assembliesillustrated in FIG. 1.

FIG. 3 is a partial sectional perspective view of the exemplary burnerassembly including a plurality of the preferred mixing tube assembliesillustrated in FIGS. 1 and 2.

FIG. 4 is an end view of the exemplary mixing section including aplurality of the preferred mixing tube assemblies illustrated in FIGS. 1through 3.

FIG. 5 is a perspective view of the exemplary mixing section including aplurality of the preferred mixing tube assemblies illustrated in FIGS. 1through 4.

FIG. 6 is a perspective view of the exemplary mixing section including aplurality of the preferred mixing tube assemblies illustrated in FIGS. 1through 5.

FIG. 7 is a perspective view of a conventional mixing tube showing theconcentration of gaseous fuel across a cross-sectional plane 28 inchesdownstream from the inlet end.

FIG. 8 is a perspective view of the preferred mixing tube assemblyillustrated in FIGS. 1-6 showing the concentration of gaseous fuelacross a cross-sectional plane 24 inches downstream from the inlet end.

FIG. 9 is a chart illustrating the concentration of gaseous fuel atdifferent radial distances for a conventional mixing tube and thepreferred mixing tube assembly illustrated in FIGS. 1-6 and 8.

FIG. 10 is a perspective front view of a first alternative embodiment ofthe preferred linear mixing tube in accordance with the presentinvention.

FIG. 11 is a perspective sectional front view of the first alternativeembodiment of the preferred linear mixing tube illustrated in FIG. 10.

FIG. 12 is a sectional front view of the first alternative embodiment ofthe preferred linear mixing tube illustrated in FIGS. 10-11.

FIG. 13 is a right side view of the first alternative embodiment of thepreferred linear mixing tube illustrated in FIGS. 10-12.

FIG. 14 is a left side view of the first alternative embodiment of thepreferred linear mixing tube illustrated in FIGS. 10-13.

FIG. 15 is a perspective front view of an exemplary mixing sectioncomprising a plurality of the first alternative embodiment of thepreferred linear mixing tubes illustrated in FIGS. 10-14.

FIG. 16 is a perspective partial sectional front view of an exemplaryburner assembly comprising the preferred mixing section illustrated inFIG. 15.

FIG. 17 is a partial sectional front view of the exemplary burnerassembly comprising the preferred mixing section illustrated in FIGS.15-16.

FIG. 18 is a right side view of the first alternative embodiment of theexemplary burner assembly comprising the preferred mixing sectionillustrated in FIGS. 15-17.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

Referring now to the drawings, the preferred embodiment of the apparatusand method for a mixing tube assembly in accordance with the presentinvention is illustrated by FIGS. 1 through 6, 8 through 18. As shown inFIGS. 1-18, the preferred embodiments of the apparatus and method for amixing tube assembly are adapted to mix air and fuel in a burnerassembly that reduces the size and cost of manufacture and operation.The preferred embodiments of the apparatus and method for a mixing tubeassembly are also adapted to mix air and fuel more efficiently,completely and uniformly.

Referring now to FIG. 1, a perspective view of the preferred mixing tubeassembly in accordance with the present invention is illustrated. Asshown in FIG. 1, the preferred mixing tube assembly is designatedgenerally by reference numeral 20. Preferred mixing tube assembly 20 hasinlet end 22 and outlet end 24. Preferred mixing tube assembly 20 isadapted for use in a burner assembly such as a gaseous burner assembly,however, it is contemplated within the scope of the invention that themixing tube assembly could be adapted for use in other suitable items ofequipment or applications. Preferred mixing tube assembly 20 comprisessubstantially cylindrical outer wall 26 which defines interior openspace 28. Preferred mixing tube assembly 20 further comprises turbulator30. Preferred turbulator 30 is disposed in interior open space 28defined by substantially cylindrical outer wall 26.

Still referring to FIG. 1, preferred substantially cylindrical outerwall 26 of mixing tube assembly 20 includes inlet end flare 32.Preferred inlet end flare 32 of substantially cylindrical outer wall 26is disposed at inlet end 22 of mixing tube assembly 20. Preferredturbulator 30 is disposed in inlet end 22 of mixing tube assembly 20.Further, preferred turbulator 30 comprises swirler 34. Preferred swirler34 is disposed in inlet end flare 32 of substantially cylindrical outerwall 26 and comprises plurality of curved vanes 36. Preferably, swirler34 is attached to plurality of tabs 38. Preferred plurality of tabs 38are disposed in inlet end 22 of mixing tube assembly 20 and attached toretainer ring 40 which is also disposed in the inlet end of the mixingtube assembly. Preferred turbulator 30 also comprises bluff body 42.Preferred bluff body 42 is spaced apart from substantially cylindricalouter wall 26 and disposed in inlet end 22 of mixing tube assembly 20.Preferred bluff body 42 is also attached to swirler 34, however, it iscontemplated within the scope of the invention that the bluff body isnot attached to the swirler.

Referring now to FIG. 2, a partial sectional perspective view ofexemplary burner assembly 50 including a plurality of preferred mixingtube assemblies 20 is illustrated. As shown in FIG. 2, the preferredplurality of mixing tube assemblies 20 are disposed in mixing section 52of burner assembly 50. Preferred mixing section 52 further comprisesinlet end tube sheet 54. While preferred mixing section 52 comprises aplurality of mixing tube assemblies 20, it is contemplated within thescope of the invention that mixing section 52 comprises only one mixingtube assembly.

Referring now to FIG. 3, a partial sectional perspective view ofexemplary burner assembly 50 including a plurality of preferred mixingtube assemblies 20 is illustrated. As shown in FIG. 3, preferred mixingsection 52 comprises inlet end flare 32, swirler 34, tabs 38, bluff body42 and inlet end tube sheet 54.

Referring now to FIG. 4, an end view of exemplary mixing section 52including a plurality of the preferred mixing tube assemblies 20 isillustrated. As shown in FIG. 4, preferred mixing section 52 includesinlet end flare 32, swirler 34, bluff body 42 and inlet end tube sheet54.

Referring now to FIG. 5, a perspective view of exemplary mixing section52 including a plurality of the preferred mixing tube assemblies 20 isillustrated. As shown in FIG. 5, preferred mixing section 52 includesinlet end flare 32, swirler 34, bluff body 42 and inlet end tube sheet54.

Referring now to FIG. 6, a perspective view of exemplary mixing section52 including a plurality of the preferred mixing tube assemblies 20 isillustrated. As shown in FIG. 6, preferred mixing section 52 includesoutlet end 24 of mixing tube assemblies 20 and outlet end tube sheet 56.

Referring now to FIG. 7, a perspective view of a conventional mixingtube showing the concentration of gaseous fuel across a cross-sectionalplane 28 inches downstream from inlet end 62 is illustrated. As shown inFIG. 7, the conventional mixing tube is designated generally byreference numeral 60. Conventional mixing tube 60 causes theconcentration of gaseous fuel within the tube to increase near the outerwall and to decrease near the center of the tube.

Referring now to FIG. 8, a perspective view of preferred mixing tubeassembly 20 showing the concentration of gaseous fuel across across-sectional plane 24 inches downstream from inlet end 22 isillustrated. As shown in FIG. 8, preferred mixing tube assembly 20causes the concentration of gaseous fuel within the tube to more uniformand in a shorter distance than conventional mixing tube 60.

Referring now to FIG. 9, a chart illustrating the concentration ofgaseous fuel at different radial distances for conventional mixing tube60 and the preferred mixing tube assembly 20 is illustrated. As shown inFIG. 9, the chart is generally designated by reference numeral 70. Asshown in chart 70, points 72 represent the gas concentration atdifferent radial distances in conventional mixing tube 60 and points 74represent the gas concentration at different radial distances inpreferred mixing tube 20. More particularly, chart 70 illustrates themass fraction of methane at radial units (meters) at 28 inchesdownstream from inlet end 62 of conventional mixing tube 60 and at 24inches downstream from inlet end 22 of preferred mixing tube assembly20.

Referring now to FIG. 10, a perspective front view of a firstalternative embodiment of the preferred linear mixing tube in accordancewith the present invention is illustrated. As shown in FIG. 10, thepreferred linear mixing tube is designated generally by referencenumeral 100. Preferred linear mixing tube 100 is adapted to straightenthe flow of the air and fuel mixture before it exits the tube so as tominimize or eliminate turbulence between flows from adjacent tubes. Moreparticularly, preferred linear mixing tube 100 comprises inlet end 102and outlet end 104. Preferred linear mixing tube 100 also comprises flowstraightening device 106 which is adapted to straighten the flow of theair and fuel mixture in the mixing tube assembly. Preferably, flowstraightening device 106 is disposed adjacent to outlet end 104 andinside outer sleeve 108. While FIG. 10 illustrates the preferredconfiguration and arrangement of the flow straightening device, it iscontemplated within the scope of the invention that the flowstraightening device may be of any suitable configuration andarrangement.

Referring now to FIG. 11, a perspective front view of preferred linearmixing tube 100 is illustrated. As shown in FIG. 11, preferred linearmixing tube 100 comprises inlet end 102, outlet end 104, flowstraightening device 106, and outer sleeve 108. Preferred linear mixingtube 100 also comprises turbulator 110. Preferably, turbulator 110 isdisposed adjacent to inlet end 102, and flow straightening device 106 isdisposed downstream from turbulator 110. Preferred turbulator 110 isadapted to uniformly and completely mix air and fuel in a burnerassembly. While FIG. 11 illustrates the preferred configuration andarrangement of the turbulator, it is contemplated within the scope ofthe invention that the turbulator may be of any suitable configurationand arrangement.

Referring now to FIG. 12, a partial sectional front view of preferredlinear mixing tube 100 is illustrated. As shown in FIG. 12, preferredlinear mixing tube 100 comprises inlet end 102, outlet end 104, flowstraightening device 106, outer sleeve 108, and turbulator 110.

Referring now to FIG. 13, a right end view of preferred linear mixingtube 100 is illustrated. As shown in FIG. 13, preferred linear mixingtube 100 comprises flow straightening device 106, outer sleeve 108, andturbulator 110.

Referring now to FIG. 14, a left end view of preferred linear mixingtube 100 is illustrated. As shown in FIG. 14, preferred linear mixingtube 100 comprises flow straightening device 106 and turbulator 110.

Referring now to FIG. 15, a perspective front view of an exemplarymixing section comprising a plurality of preferred linear mixing tubes100 is illustrated. As shown in FIG. 15, the exemplary mixing section isdesignated generally by reference numeral 116. Exemplary mixing section116 comprises linear mixing tubes 100 having inlet ends 102, outlet ends104, and flow straightening devices 106. Exemplary mixing section alsocomprises inlet end tube sheet 112 and outlet end tube sheet 114. WhileFIG. 15 illustrates the preferred configuration and arrangement of theexemplary mixing section comprising a plurality of preferred linearmixing tubes, it is contemplated within the scope of the invention thatthe mixing section may be of any suitable configuration and arrangement.

Referring now to FIG. 16, a perspective partial sectional front view ofan exemplary burner assembly comprising preferred mixing section 116 isillustrated. As shown in FIG. 16, the exemplary burner is designatedgenerally by reference numeral 118. Preferred burner assembly 118comprises longitudinal axis 120. Preferably, flow straightening devices106 are adapted to facilitate the flow of the air and fuel mixture in adirection that is generally parallel to longitudinal axis 120 of burnerassembly 118.

Referring now to FIG. 17, a partial sectional front view of exemplaryburner assembly 118 comprising preferred mixing section 116 isillustrated. As shown in FIG. 17, exemplary burner assembly comprises anupstream end 122 and a downstream end 124. Preferably, the turbulatorsare disposed closer to upstream end 122 than the flow straighteningdevices, and the flow straightening devices are disposed closer todownstream end 124 than the turbulators.

Referring now to FIG. 18, a right end view of exemplary burner assembly118 comprising preferred mixing section 116 is illustrated. While FIGS.16-18 illustrate the preferred configuration and arrangement of theburner assembly and mixing section, it is contemplated within the scopeof the invention that the burner assembly and mixing section may be ofany suitable configuration and arrangement.

The invention also comprises a method for mixing fuel and air in aburner assembly. The preferred method comprises providing a mixing tubeassembly having an inlet end and an outlet end. The preferred mixingtube assembly comprises a substantially cylindrical outer wall whichdefines an interior open space. The preferred mixing tube assembly alsocomprises a turbulator that is disposed in the interior open spacedefined by the substantially cylindrical outer wall and a flowstraightening device that is disposed downstream from the turbulator.The preferred method also comprises conveying fuel and air from theinlet end of the mixing tube assembly to the outlet end of the mixingtube assembly.

In another preferred embodiment, the method comprises a turbulatorhaving a retainer ring that is disposed at the inlet end of the mixingtube assembly, a plurality of tabs that are attached to the retainerring, a swirler that is attached to the plurality of tabs and a bluffbody that is attached to the swirler. In still another preferredembodiment, the method comprises mixing gaseous fuel and air in themixing tube assembly, and straightening the gaseous fuel and air mixtureflow in the mixing tube assembly.

In operation, several advantages of the preferred embodiments of theinvention are achieved. For example, the preferred embodiments of theapparatus and method for a mixing tube assembly are adapted to mix airand fuel in a burner assembly that reduces the size and cost ofmanufacture and operation. The preferred embodiments of the apparatusand method for a mixing tube assembly are also adapted to mix air andfuel more efficiently, completely and uniformly. Further, the preferredembodiments of the apparatus and method for a mixing tube assembly areadapted to straighten the gaseous fuel and air mixture flow in themixing tube so as to minimize or eliminate turbulence between flows fromother mixing tube assemblies.

Although this description contains many specifics, these should not beconstrued as limiting the scope of the invention but as merely providingillustrations of some of the presently preferred embodiments thereof, aswell as the best mode contemplated by the inventors of carrying out theinvention. The invention, as described herein, is susceptible to variousmodifications and adaptations, and the same are intended to becomprehended within the meaning and range of equivalents of the appendedclaims.

What is claimed is:
 1. A mixing section adapted for use in a burnerassembly, said mixing section comprising a plurality of mixing tubeassemblies, each of said mixing tube assemblies having an inlet end andan outlet end and comprising: (a) a substantially cylindrical outerwall, said substantially cylindrical outer wall defining an interioropen space; (b) a turbulator, said turbulator being disposed in theinterior open space defined by the substantially cylindrical outer wall;and (c) a flow straightening device, said flow straightening devicebeing disposed downstream from the turbulator; wherein each turbulatoris substantially surrounded by one substantially cylindrical outer walland each substantially cylindrical outer wall substantially surroundsone turbulator; and wherein each mixing tube assembly is adapted toreceive fuel downstream from the turbulator; and wherein each of theplurality of mixing tube assemblies separately mixes an amount of fueland air; and wherein the mixing section is adapted to produce a mixtureof fuel and air; and wherein at least one of the turbulators comprises aswirler; and wherein the swirler comprises a plurality of curved vanes.2. The mixing section of claim 1 wherein each of the substantiallycylindrical outer walls has an inlet end flare.
 3. The mixing section ofclaim 2 wherein each of the inlet end flares of each of thesubstantially cylindrical outer walls is disposed at the inlet end ofone of the plurality of mixing tube assemblies.
 4. The mixing section ofclaim 1 wherein each of the turbulators is disposed in the inlet end ofone of the plurality of mixing tube assemblies.
 5. The mixing section ofclaim 1 wherein the swirler is disposed in the inlet end of the at leastone of the plurality of mixing tube assemblies.
 6. The mixing section ofclaim 1 wherein the swirler is attached to a plurality of tabs.
 7. Themixing section of claim 6 wherein the plurality of tabs are disposed inthe inlet end of at least one of the plurality of mixing tubeassemblies.
 8. The mixing section of claim 6 wherein the plurality oftabs are attached to a retainer ring disposed in the inlet end of the atleast one of the plurality of mixing tube assemblies.
 9. The mixingsection of claim 1 wherein at least one of the turbulators comprises abluff body.
 10. The mixing section of claim 9 wherein each of the bluffbodies is spaced apart from the substantially cylindrical outer wallthat substantially surrounds said bluff body.
 11. The mixing section ofclaim 9 wherein each of the bluff bodies is disposed in the inlet end ofone of the plurality of the mixing tube assemblies.
 12. The mixingsection of claim 1 wherein the mixing section further comprises a tubesheet.
 13. A mixing section adapted for use in a gaseous burnerassembly, said mixing section comprising a plurality of mixing tubeassemblies, each of said mixing tube assemblies having an inlet end andan outlet end and comprising: (a) a substantially cylindrical outerwall, said substantially cylindrical outer wall defining an interioropen space and having an inlet end flare; (b) a turbulator, saidturbulator being disposed in the interior open space defined by thesubstantially cylindrical outer wall and comprising: (1) a retainerring, said retainer ring being disposed at the inlet end of the mixingtube assembly; (2) a plurality of tabs, said plurality of tabs beingattached to the retainer ring; (3) a swirler, said swirler beingattached to the plurality of tabs; (4) a bluff body, said bluff bodybeing attached to the swirler; (c) a flow straightening device, saidflow straightening device being disposed downstream from the turbulator;wherein each turbulator is substantially surrounded by one substantiallycylindrical outer wall and each substantially cylindrical outer wallsubstantially surrounds one turbulator; and wherein each mixing tubeassembly is adapted to receive fuel downstream from the turbulator; andwherein each of the plurality of mixing tube assemblies separately mixesan amount of fuel and air; and wherein the mixing section is adapted toproduce a mixture of fuel and air.
 14. A method for mixing fuel and airin a burner assembly, said method comprising: (a) providing a mixingsection adapted for use in the burner assembly, said mixing sectioncomprising a plurality of mixing tube assemblies, each of said mixingtube assemblies having an inlet end and an outlet end and comprising:(1) a substantially cylindrical outer wall, said substantiallycylindrical outer wall defining an interior open space; (2) aturbulator, said turbulator being disposed in the interior open spacedefined by the substantially cylindrical outer wall, and each of saidturbulators comprising: (i) a retainer ring, said retainer ring beingdisposed at the inlet end of the mixing tube assembly; (ii) a pluralityof tabs, said plurality of tabs being attached to the retainer ring;(iii) a swirler, said swirler being attached to the plurality of tabs;(iv) a bluff body, said bluff body being attached to the swirler; (3) aflow straightening device, said flow straightening device being disposeddownstream from the turbulator; and wherein each turbulator issubstantially surrounded by one substantially cylindrical outer wall andeach substantially cylindrical outer wall substantially surrounds oneturbulator; and wherein each mixing tube assembly is adapted to receivefuel downstream from the turbulator; and wherein each of the pluralityof mixing tube assemblies separately mixes an amount of fuel and air;and (b) conveying fuel and air from the inlet end of the mixing tubeassembly to the outlet end of the mixing tube assembly.
 15. The methodof claim 14 further comprising: (c) mixing gaseous fuel and air in theplurality of mixing tube assemblies; and (d) straightening the gaseousfuel and air mixture flow in the mixing tube assembly.